E3 S Web of Conferences8, 01042 (2016) DOI: 10.1051/ e3 sconf /201600108 42 MEC2016 Flotation of zinc and lead oxide minerals from Olkusz region calamine ores Krystian Cichy1,a, Cezary Regula2 and Grazyna Pajor2 1Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100 Gliwice, Poland 2ZGH “Boleslaw” S.A., Poland Abstract. The paper presents chemical and mineralogical characteristics of calamine ore from the Pomorzany mine. A flowsheet for recovery of sulphide minerals of zinc and lead in the form of the Zn-Pb bulk concentrate was presented. In the following part, preparation of the feed for flotation of Zn-Pb oxide minerals and optimal conditions for separation from it iron sulphide minerals, represented by marcasite, were determined. In the final section the results of flotation of Zn-Pb oxide minerals with anionic collector AM2 belonging to the hydroxyamide group of collectors and a cationic collector in the form of a coconut amine, being a mixture of primary aliphatic amines, were presented. Basing on the obtained results, a technological flowsheet for the recovery of Zn-Pb sulphide and oxide minerals from the calamine ore of the Pomorzany mine was presented. 1 Introduction Lead and zinc was produced in Poland from calamine ores by using the Waelz process. The extracted ore was subjected to roasting in the presence of coke as a reducing agent. As a result the so-called raw zinc oxide, which was the raw material for production of metallic zinc and lead was achieved. The high costs of the process were the reason for stopping, in the early 90-ies of the twentieth century, production of lead and zinc from the calamine ore using this method. The calamine ores are the final results of transformation of sulphide deposits of Zn-Pb under the influence of surface water enriched in oxygen. The zinc and lead minerals are usually in the form of carbonate minerals such as smithsonite and monheimite (zinc) and cerussite (lead). Their formation is a result of reaction of acidic sulphate solutions arising from oxidation of metal sulphides contained in the ore with the surrounding carbonate rocks such as calcite and dolomite. As a result formation of secondary carbonate minerals of zinc and lead takes place. Due to the similarity of surface properties of carbonate minerals of zinc and lead to the surrounding waste rock, which is mostly dolomite, their flotation has not yet been sufficiently resolved. So far, the studies have shown that the only practical flotation method of oxide ore of Zn-Pb beneficiation is the so-called Rey method involving sulphidizing the surfaces of minerals by sodium sulphide and their flotation with primary aliphatic amines having the hydrocarbon chain length of C12- C16. [1, 2] a Corresponding author: [email protected] © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3 S Web of Conferences8, 01042 (2016) DOI: 10.1051/ e3 sconf /201600108 42 MEC2016 Due to the fact that the surface of carbonate minerals has in aqueous medium a negative charge and amine is a cationic collector, it is necessary to separate slimes from the feed prior to flotation because the cationic collector can be adsorbed by the electrostatic forces and it will finally result in transfer the slimes to the froth product. The necessity of the initial desliming of the feed significantly reduces in practice the range of application of this method due to high losses of metals in the removed slime fraction. Another disadvantage of this method is a good collecting ability of aliphatic amines with respect to the sulphide minerals of iron, which have, as natural sulphides, under these conditions, much better floatability than sulphidized carbonate minerals of Zn-Pb. The necessity of the initial desliming of the feed and flotation of iron sulphide minerals considerably reduces the use of this method due to the high losses of metals in the removed products. Its use can be economically justified only in case of enriching the very rich Zn-Pb oxide ores. The aim of this study is to investigate whether flotation recovery of Zn-Pb oxide minerals is possible with other than amines collectors, which do not require costly and troublesome sulphidation. 2 Characteristics of studied ore The subject of research was the calamine ore from the Pomorzany mine which is currently the only active mine in Poland that extracts the Zn-Pb ore. The chemical analysis of studied ore is shown in Table 1. Table 1. Chemical analysis of studied calamine ore from the Pomorzany mine. Content, % Zn Zn(O) Zn(S) Pb Pb(O) Pb(S) Fe Fe(O) Fe(S) CaO MgO 5.58 3.61 1.97 0.95 0.73 0.23 43.70 29.93 13.77 2.44 0.93 The chemical analysis indicates that the tested ore is almost an iron ore with significant additions of zinc and lead, in which there is practically no waste rock. A basic mineralogical composition of the ore is as follows: Mineral Distribution, % galena 0.3 cerussite 1.0 sphalerite 2.9 marcasite 29.6 monheimite 13.3 goethite 46.8 dolomite 6.2 Sum 100.0% The main mineral in the studied ore is goethite constituting nearly 47% of the composition, while the second the most abundant component is marcasite, which is sulphide mineral of iron in the amount of approx. 29.6%. In total iron minerals constitute more than 76% of the ore. The main zinc minerals are monheimite and sphalerite occurring in amounts of approx. 13.3% and 2.9%, while lead minerals are cerussite and galena in the amounts of approx. 1.0% and 0.3%. Such a composition of the ore shows that the basic difficulty in the process of enrichment is the presence of iron oxide minerals represented by goethite forming the smallest particles of slime. 2 E3 S Web of Conferences8, 01042 (2016) DOI: 10.1051/ e3 sconf /201600108 42 MEC2016 3 Determination of the optimal conditions for the recovery of zinc and lead sulphide minerals Flotation concentrate containing Zn-Pb oxide minerals can be directed for processing by the Waelz process provided that firstly the Zn-Pb sulphide minerals are removed, because their presence in the process is undesirable due to the sulphur content. Accordingly, the first step is to determine the optimal conditions for flotation of galena and blende. Due to a significant amount of goethite, which is a potential source of slime fraction generated in grinding, the ore grinding is limited to the standard particle size <0.2 mm carried out in a laboratory rod mill. The analysis of particle size distribution and chemical content of feed for flotation is given in Table 2. Table 2. Analysis of particle size distribution of feed for flotation. Content, % Grain class Yield mm % %Zn(O) %Pb(O) Zn Zn(O) Pb Pb(O) Fe Zn Pb > 0.2 4.32 5.30 3.31 62.45 0.91 0.73 80.22 43.70 0.2 – 0.1 10.28 6.80 4.03 59.26 0.76 0.62 81.60 39.40 0.1– 0.071 10.32 6.20 3.84 61.94 0.95 0.70 74.01 46.17 0.071-0.035 14.00 5.47 3.41 62.30 1.00 0.76 76.14 43.15 < 0.035 61.08 5.34 3.62 67.79 0.96 0.69 71.70 42.25 Sum 100.00 5.60 3.64 65.09 0.94 0.70 73.77 42.55 The presented particle size distribution shows that in the feed for flotation there is a significant amount of ultrafine grains <0.035 mm of approx. 60%, which is the result of overgrinding of goethite. A small amount of galena in the studied ore was the reason for separation of the Zn-Pb sulphide minerals in the collective enrichment flowsheet. The study of bulk flotation process was conducted in the laboratory pneumatic-mechanical flotation machine of IZ type with a chamber volume of 2.5 l. In the first stage, the tests of the bulk flotation of galena and blende were carried out with the feed without desliming, and in the next stage with the deslimed feed. Desliming was performed in a laboratory hydrocyclone 50 mm with particle cutsize of approx. 10 m. The flotation conditions were as follows: density 400 g/l, CuSO4 350 g/t, NaX iso-amyl 25 g/t, Mileflot X-23 15 g/t, 20 g/t and 25 g/t, Corflot 5 g/t, flotation time 15 min. Table 3 presents the results of the preformed tests of Zn-Pb bulk flotation. Table 3. Results of bulk flotation of Zn-Pb sulphide minerals from the feed not deslimed and after desliming. Flotation Yield Content, % Recovery, % Product conditions %ZnPbFeZnPbFe Feed 100.00 5.52 0.94 43.36 100.00 100.00 100.00 Not deslimed feed C ZnS + PbS 13.26 8.42 0.90 37.40 20.23 12.70 11.44 T ZnS + PbS 86.74 5.08 0.95 44.27 79.77 87.30 88.56 Feed 100.00 5.54 0.96 43.92 100.00 100.00 100.00 Slime 15.76 5.30 1.03 42.00 15.08 16.91 15.07 Deslimed feed HC underflow 84.24 5.58 0.95 44.28 84.92 83.09 84.93 C ZnS + PbS 7.52 23.37 1.62 28.95 31.73 12.69 4.96 T ZnS + PbS 76.72 3.84 0.88 45.78 53.19 70.40 79.97 3 E3 S Web of Conferences8, 01042 (2016) DOI: 10.1051/ e3 sconf /201600108 42 MEC2016 The introduction of desliming operation resulted in a significant improvement of the enrichment indices, both in terms of improving concentrate quality and metals recovery.For determination of the final indices of recovery of Zn-Pb sulphide minerals corresponding to the industrial conditions, the flotation tests were carried out using the flowsheet with the cleaning flotations to obtain Zn-Pb concentrate as in commercial operation.